FIGS. 1 and 2 represent the prior art. Referring to FIGS. 1 and 2, a valve housing 10 has control lines 12 and 14 that extend to opposite sides of piston 16. Piston 16 is connected to insert sleeve 18 for tandem movement. Insert sleeve 18 has a hole pattern 20 that moves up and down into and out of alignment with openings 22 in the housing 10. Seals 24 and 26 straddle ports 22 so that when openings 20 are not between seals 24 and 26 the valve is fully closed. On the other hand when the ports 20 are between seals 24 and 26, as shown in FIG. 1, then the valve is in the diffused position where some flow is possible between ports 20 and 22 through diffuser 28. Alternating pressure application between lines 12 and 14 forces relative movement of pin 30 in the j-slot pattern 32. A series of stair step travel stops 34 define how much more open the valve gets in each pressure cycle. The other half of each cycle has the lug 36 landing on the same spot 38 to define the diffused position shown in FIG. 1. In each pressure cycle, the lug 36 lands on a different step 34 to represent another opening increment. After a predetermined number of cycles the lug 36 can go to landing 40 for a fully closed position where the openings 20 are no longer between seals 24 and 26. In the very next cycle it can go to fully open when lug 36 is allowed to keep traveling by slot 41 until it hits stop 42. These FIGS. are from U.S. Pat. No. 8,186,439.
Notable in this design are the fact that the pin 30 is not load bearing. Instead, the load is taken up by lug 36 landing at 38 for the diffused position and steps 34 to define the various percent open positions of the illustrated choke. As a result of this design where the pin 30 takes no load but is used to simply create rotation to move the valve into intermediate positions, there are long pin travel slots 44 and 46 that enable such action but as a result due to limited stroke length of piston 16 the opposed peaks 48 and 50 are brought very close to each other. If fully cycling through the various positions there is normally no jamming problem. Jamming can occur if there is a partial piston stroke followed by a reversal of the movement which can land the pin 30 on the peak such as 50 that the pin just passed. This can deform the pin to an extent that further stroking of the piston 16 can be to no avail as the valve will jam. The close fit of the peaks 48 and 50 gives surface personnel little time to respond to prevent such a jamming situation when there is a partial stroke.
The present invention employs a load bearing lug that preferably has angled end surfaces and more preferably has a trapezoidal shape. The opposed ramp profile has a generally mating shape to the lug opposed ends. Because of this feature allowing the elimination of the axial travel slots for the pin 30 in the prior art the opposed patterns that define the j-slot profile can be placed further apart for the same piston stroke capability. Placing the opposed mating patterns further apart allows more time in a partial stroke situation for the operator to react and back off the movement before that critical alignment occurs that can jam the valve. By having the extra time to react due to the enhanced spacing which increases axial peak to peak distance from about ⅛″ to over 3″ more of a partial stroke can be accomplished with the ability to back off the stroke without jamming. Shorter enlarged distances that still exceed the prior peak distance of ⅛″ are also contemplated. While jamming is still possible with a partial stroke, the potential for the jamming having been moved to near the end of the full stroke from very near the beginning of the full stroke as in the prior art allows the surface personnel reaction time that could be instrumental in avoiding a jam situation altogether. There is no incremental increase in tool length due to the peak to peak separation as the load bearing lug allows for the elimination of the axial travel slots on one side of the pattern. Open slots on the other side are envisioned to allow assembly of the lug between the patterns and to allow needed positions for the subterranean tool. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.